Safety systems for aircraft passenger or crew seats have been devised. See for example U.S. Pat. No. 4,523,730.
Generally such systems are characterized by a seat slidably mounted with respect to the floor of the aircraft. The sliding movement of the seat is restricted by the provision of a deformable rod or pipe. Energy absorption in a crash situation is accomplished by die means adapted to squeezably deform the rod or pipe as the crash seat descends under the extreme load experienced in a crash.
One of the major deficiencies experienced in this type of aircraft crash seat resides in that while the kinetic crash energy developed increases proportionately to the weight of the seat occupant, the energy absorption capacity of seat safety system is essentially constant and not readily adjustable. Thus a relatively heavy occupant will exceed the energy absorbing capacity of the seat system and remain unprotected towards the end of the sliding movement thereof, whereas relatively lightweight passengers will not optimally exploit the energy absorbing capability of the system along the entire stroke of the seat between its normal and crash induced positions.
To remedy this deficiency, certain improvements have been devised involving manual adjustment of the system for optimalization correspondent to the individual conditions under which it is to be operable. According to such conventional systems, at some time prior to crash, generally before take-off, the occupant must manually adjust the system in order to adapt it to his weight.
Obviously, such adjustments are inconvenient and cumbersome, and are particularly inapplicable to multi-passenger seats used in normal air passenger traffic.
Additionally, it is known that in many crash situations, prior to impact, aircraft take evasive action including braking and attempts to pull out of the crash. Such maneuvering results in the application of various accelerative forces to the aircraft affecting the relative weight of the seat occupant, and possibly impacting on the occupant weight induced self optimalization of the system.
Thus it is the general object of the invention to provide an impact energy absorption system for aircraft seats being self-adjusting with respect to the individual conditions, namely the weight of the occupant or occupants of the seat.
It is a further object of the invention to effect impact energy absorption by incorporation of variable rod deforming means in addition to the initial, conventional die means.
It is a still further object of the invention to provide inertia responsive means to isolate the weight induced self adjustment of impact energy absorption capacity from the effects of accelerative forces expereienced during pre-crash maneuvering.